This invention relates to a method and apparatus for extraction of mercury and gold from mine tailings.
In recent years effective centrifugal separating devices have become available for more effective separation of heavy materials including gold from particulate mineral feed. The feed is graded to a required particulate size for feeding into the centrifuge bowl and is mixed with water to form a flowing slurry which can pass into the bowl for reaction of high centrifugal force to cause effective and efficient separation. One machine of this type is manufactured by a company associated with the present inventor and in one embodiment of that machine is shown in detail in U.S. Pat. No. 4,846,781 issued Jul. 11, 1989. Further details of the same machine are shown in U.S. Pat. No. 4,776,833 issued Oct. 11, 1988 and U.S. Pat. No. 4,608,040 issued Aug. 26, 1986. Reference to the detail shown in these patents should be made by the reader for any points omitted herein or requiring further explanation.
One particular field of use for the above machine is that of retreatment of mine tailings to extract gold which has previously remained in the tailings or rejected materials due to the inefficiency of the process used at the time of separation.
In addition to the gold present in the tailings there is also in many cases a significant quantity of mercury which has been released into the environment from the processes used at the time of the original mining procedure. This mercury is of course a significant contaminant to the environment and is highly desirable to clean up or extract the mercury at the same time as extracting the valuable gold content.
The above machine of the present inventor is highly effective in separating the gold content. However it has been found that it does not effectively extract and collect the mercury content and this is rereleased into the mine tailings. The machine thus extracts the valuable content but cannot at the same time effect the desirable environmental clean up. As the mercury is in liquid form it tends to escape from the bowl and reenter the tailings.
A number of previous machines have been proposed for continuous separation of a heavier component from a light component and examples of these are shown in U.S. Pat. No. 1,473,421 (Eccleston); U.S. Pat. No. 1,283,846 (Mark et al); U.S. Pat. No. 1,557,672 (Doerner); U.S. Pat. No. 3,192,149 (Keith); U.S. Pat. No. 4,966,576 (Schultz et al); U.S. Pat. No. 1,190,466 (Schifferie); U.S. Pat. No. 2,723,799 (Sharples); 957478 (Simpson) and U.S. Pat. No. 1,594,501 (Eccleston). However none of these patents relate to the separation of the heavies including gold in solid form and the separate extraction of mercury in liquid form, all separate from the light materials which are discarded.